JPH02224413A - 2-1 selector circuit - Google Patents

Abstract

PURPOSE:To make an input signal and an output signal coincide with each other even at the time of the switching of a selected signal by releasing the gate of an unselected signal at first before the selected signal is switched at the time of the switching of the selected signal, and controlling the gate for gating an unselected input signal after the switching of the selected signal. CONSTITUTION:A gate control circuit 11 controls gate circuits 12a, 12b so as to gate an input signal A or B according to the state of the selected signal S, and makes the ungated signal of the signal A or B into the signal Y by an OR element 13. For instance, when the signal S is in a 'low' state, the gate control circuit 11 controls the gate circuit 12b to gate the signal B, and makes the signal A into the signal Y through the gate circuit 12a and the OR circuit 13. when the signal S changes from the 'low' state to a 'high' state, it releases the gating of the signal B by the gate circuit 12b. Then, it transmits the signal B to the OR circuit 13 through the gate circuit 12b, and makes the signal Y the signal A or B.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a 2-1 selector circuit that selects and outputs one desired input signal from two input signals using one selection signal, and in particular, The present invention relates to a 2-1 selector circuit that matches an input signal and an output signal even when switching selection signals.

[Prior Art] Conventionally, a circuit that selects and outputs one desired input signal from two input signals using one selection signal is called a 2-1 selector circuit. , the selection signal gates the input signal that is not selected among the two input signals.

When switching the selection signal, gates and gates are simultaneously applied to the two input signals.

[Problems to be Solved by the Invention] The conventional 2-1 selector circuit described above simultaneously gates and releases the gates for two input signals when switching the selection signal. A situation occurs where the input signals are gated simultaneously. At this time, there is a drawback that the input signal and the output signal do not match, resulting in the generation of an erroneous signal in the entire circuit.

[Means for Solving the Problems] An object of the present invention is to solve the problems of the prior art described above, and to provide a 2-1 selector circuit that can match the input signal and the output signal even when switching the selection signal. It is to provide.

The present invention has achieved the above object, and provides a 2-1 selector circuit that selects and outputs a desired one input signal from two input signals using one selection signal. Gate control is performed to gate the input signals that are not selected, and when switching the selection signal, first, the gates of the input signals that are not selected before switching the selection signal are released, and then the gates of the input signals that are not selected after switching the selection signal are gated. a gate control circuit that performs gate control to gate the input signal; and two gate circuits that gate the input signal by gate control from the gate control circuit.
It also includes an OR circuit for making the input signal that is not gated by the gate circuit out of the two input signals into the signal selected by the selection signal, so that the input signal and the output signal can be matched even when the selection signal is switched. It is characterized by making it match.

[Example] Next, a 2-1 selector circuit according to the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of a 2-1 selector circuit according to the present invention.

In the drawings, A and B are input signals input to two input terminals 1.2 of the 2-1 selector circuit according to the present invention,
The two inputs S are selection signals input to the selection signal terminal 3 for selecting one desired input signal from No. 1.2.

11 is a gate control circuit, and a pair of NAND elements 1
1a, llb, a NOT element 11c connected between the input terminal of one NAND element 11b and the selection signal terminal, and the input terminal of each NAND element 11a, itb and the output of the other NAND element 11b, lla. It is composed of gate delay elements lid and lie connected between the terminals.

12a and 12b are a pair of AND elements and constitute a gate circuit. A pair of input terminals of each gate circuit 12a, 12b are connected to NAND elements 11b, 11. a and two input terminals 1.2 of the 2-1 selector circuit according to the invention.

13 is an OR element connected to the outputs of the pair of gate circuits n 12 a, 12b.

The gate control circuit 11 outputs either the A signal or the S signal depending on the S signal state.
The gate circuits 12a and 12b are controlled to gate the signal, and the OR element 13 converts the non-gated A signal or S signal into the Y signal.

For example, when the S signal is in a “low” state, the gate control circuit 1
1 performs control to gate the S signal by the gate circuit 12b, and converts the A signal into the Y signal through the gate circuit 12a and the OR circuit 13. When the S signal changes from the "low" state to the "high 7" state, the gate control circuit 11 first controls the gate circuit I.
Release the gate of the S signal by II 2b and make the S signal
It is transmitted to the OR circuit 13 through the gate circuit 12b, and Y
Let the signal be A signal or B signal.

Next, the gate control circuit 11 sends the B signal to the gate circuit 12.
The Y signal is transmitted to the OR circuit 13 through the gate circuit 12a, and the gate delay element lid waits for the time until the Y signal becomes the A signal or the B signal.Then, the gate circuit 12a controls the gate of the A signal to convert the Y signal to the B signal. Signal.

[Effects of the Invention] As explained above, the present invention selects one desired input signal from two input signals using one selection signal,
In the 2-1 selector circuit that outputs, the selection signal performs gate control to gate the input signal that is not selected among the two input signals, and when switching the selection signal, first, the input signal that is not selected before switching the selection signal is gated. A gate control circuit that performs gate M control to release the gate of the input signal and then gate the input signal that is not selected after switching the selection signal, and two gates that gate the input signal by gate control from the gate control circuit. Since it is equipped with an OR circuit for making the input signal that is not gated by the gate circuit out of the two input signals into the signal selected by the selection signal, even when switching the selection signal, the input signal This has the effect of making it possible to match the output signal with the output signal.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of a 2-1 selector circuit according to the present invention. 1.2... Input terminal 3... Selection signal terminal 11... Gate control circuit 11a, flb-NAND element 11c = NOT element lid, lie... Gate delay elements 12a, 12b... Gate circuit 13 ...OR element

Claims (1)

[Claims] In a 2-1 selector circuit that selects and outputs one desired input signal from two input signals using one selection signal, the selection signal selects an input signal that is not selected from among the two input signals. When the selection signal is switched, firstly, the gate of the input signal that is not selected is released before the selection signal is switched, and then the gate is used to gate the input signal that is not selected after the selection signal is switched. A gate control circuit that performs control, two gate circuits that gate input signals by gate control from the gate control circuit, and a selection signal that gates the input signal that is not gated by the gate circuit among the two input signals. A 2-1 selector circuit comprising: an OR circuit for making a selected signal, thereby making an input signal and an output signal match even when switching the selection signal.